1. Field of the Invention
This invention relates generally to side printing on a laminated assembly of low temperature co-fired ceramic (LTCC) material, and more particularly to a method and apparatus for side printing on an LTCC substrate for microwave transmit/receive (T/R) modules which are used in connection with an active aperture of a phased array radar system.
2. Description of Related Art
The conventionally used screen printers cannot accommodate the newly designed LTCC substrates because of height restrictions associated with the screen printers and because of the currently used hold down mechanisms for the substrates.
Conventional T/R module packages include a structure utilizing a multi-cavity and a multi-layer substrate as shown, for example, in U.S. Pat. No. 6,114,986, comprised of high temperature co-fired ceramic (HTCC) layers including, for example, black alumina ceramics and tungsten. The ceramic layers have outer surfaces including metallization patterns of ground planes and conductors as well as feedthroughs or vertical vias formed therein for providing three dimensional routing of both RF and DC signals. Active circuit components comprised of integrated circuit chips are located in the various cavities of the substrate. The active circuit components are used for implementing suitable control and generating functions of RF signals to and from respective antenna elements. In addition, such HTCC designs utilize a nickel/gold plating approach.
However, a newly designed LTCC substrate such as shown and described in related application Ser. No. 10/718,805, does not accept the nickel/gold plating approach because such LTCC design, including T/R modules incorporating the same, include highly complex packages of up to 20 or more layers of tape and have multiple cavities with different floor thicknesses, through-holes, and an integrated ring frame in the package as required, for example, by an LTCC T/R module utilized in a radar system.
The newly designed LTCC T/R module referred to above utilizing such a complex package design requires that RF lines extend to the outer surface (periphery) of the LTCC substrate. The RF lines are then connected to connector pins through a brazing operation. In order for a print to be added to the RF lines, metallization must be deposited and fired on the outer side wall of the LTCC substrate. Side printing requires deposition of brazeable metallization; however, LTCC material does not accept the standard HTCC approach of using nickel/gold plating. Furthermore, attempts have been made to use standard screen printers to do side printing, however, the standard screen printers cannot accommodate a part standing on its end or a part having a thickness greater than 1″. As such, in using standard screen printers, there is no room for the part to stand nor is there any currently available method of hold down for parts thicker than 1″. Therefore, in order for the side of the LTCC substrate to be printed on, a new and improved print fixture is needed and comprises the subject matter of this invention.